From canada.com: Montreal mob boss Frank Cotroni and high-ranking U.S. mobsters were once investigated for an alleged plot to assassinate the top judge in the United States, according to newly released FBI documents.

The investigation into the alleged plot to assassinate Chief Justice Warren Burger of the U.S. Supreme Court began in December 1981 after an informant came forward with details of a jailhouse plot. It ended 15 months later with no charges being laid.

Instead, the Federal Bureau of Investigation sent agents to warn the heads of U.S. Mafia families that any attempt to assassinate Burger "would be responded to with the full force and resources of the (Department) of Justice and the FBI." Rest of Article. . . [Mark Godsey]